Fermentation methods, methods for matter production involving culturing of microorganisms or cultured cells, can be broadly classified into two types: (1) batch fermentation and fed-batch fermentation and (2) continuous fermentation.
In (2) continuous fermentation, methods have been proposed in which microorganisms or cultured cells are filtered through a separation membrane, and the microorganisms or cultured cells in a concentrate are held in or refluxed to a fermentation broth while recovering chemical products from filtrate, whereby the concentration of the microorganisms or cultured cells in the fermentation broth is maintained high.